New Delhi: As India moves towards providing precautionary doses of the Covid vaccine for its high-risk population — healthcare workers, frontline workers and people over the age of 60 with comorbidities — there is a fresh set of vaccines that will soon become available for those who are yet to get their doses.
This week, along with approving vaccination for those in the 15-18 years age group, India also gave emergency-use authorisation to two other vaccines — Corbevax and Covovax.
ThePrint explains all we know about these vaccines.
Corbevax was developed by Hyderabad-based biopharmaceutical firm Biological E., the Baylor College of Medicine in the US, and US-based company Dynavax Technologies.
Corbevax is what is known as a protein subunit vaccine. It contains a protein of the coronavirus, and the body becomes prepared to recognise and launch an immune response against this. This differs from vaccines like Covaxin, which contains the whole virus but in an inactivated form.
Corbevax contains the receptor binding domain — a region of the spike protein of the SARS-CoV-2 virus that helps it infect the host cell.
Corbevax uses a recombinant protein-based technology — a proven technology that has been in use since the 1980s and is used in the Hepatitis B vaccine. The technology involves using genetic engineering to insert a DNA code that allows a harmless microbe, such as yeast, to grow the desired protein.
For Corbevax, researchers have used the yeast Pichia pastoris to grow the receptor binding domain of the SARS-CoV-2 virus. The yeast does not cause a disease in humans, but the body learns to recognise the protein of the coronavirus. If the body encounters the real virus in future, it will immediately recognise the receptor binding domain and launch an attack.
As this vaccine — unlike Covaxin — contains only a part of the virus, it also needs an adjuvant, which is something added to vaccines to make the immune response stronger.
According to the researchers, two Phase III clinical trials of Corbevax involving more than 3,000 people showed that the vaccine is safe and effective, and that it has an efficacy of over 90 per cent, although the results are yet to be published in a peer-reviewed journal.
The vaccine developed by US-based company Novavax will be produced by the Pune-based Serum Institute of India under the name Covovax. It is also a recombinant protein-based vaccine.
To develop the vaccine, researchers selected a part of the genetic sequence of the virus that produces the spike protein. This sequence was then introduced in baculoviruses — pathogens that attack insects. So, the difference from Corbevax is that instead of using yeast, this vaccine uses baculoviruses.
These modified baculoviruses were then made to infect moth cells in the lab, so that the cells produced proteins that are similar in structure to the SARS-CoV-2 spike protein.
These proteins were then purified and administered with an adjuvant called Matrix M.
Like all vaccines, Covovax tricks the immune system into believing that it is under attack from the real virus.
Phase III trials for the Novavax vaccine have been carried out in the UK, the US, Mexico and South Africa.
The results of Phase III trials among approximately 15,000 participants in the UK, published in The New England Journal of Medicine on 23 September, found that the Novavax vaccine provided 89.7% protection against SARS-CoV-2 infection.
Along with the two new vaccines, India has also approved Molnupiravir — an antiviral that its makers say can treat people with mild and moderate Covid disease. Thirteen companies in India are set to manufacture this drug, including Cipla and Dr Reddy’s.
(Edited by Rohan Manoj)